Upstream-Downstream Drainage Issues

Think Different
“Public ditches often cause conflicts between farm neighbors,” says retired Mapleton, Minn., farmer Dick Nienow. One of the most important ways to foster cooperation on a ditch project is to get lots of landowner input early on and reserve plenty of time for planning, Nienow says. “Let growers make suggestions.” Blue Earth County Ditch Manager Craig Austinson agrees: “Landowners often feel they don’t get enough input into a ditch project before money is spent or a petition drafted.”

There’s an old adage in drainage lore: Whiskey’s for drinkin’; water’s for fightin’!

Upstream and downstream farmers along 100-year-old County Ditch 57 in Blue Earth County, in heavily tiled south-central Minnesota, started out at loggerheads over ditch improvements. But they ended up working together to improve both drainage capacity and water quality – thanks to innovative drainage methods and a determined fundraising effort by local leaders.

From its founding, Ditch 57 “has had a history of ending up in court,” says Blue Earth County Ditch Manager Craig Austinson, “so getting the landowners to come to agreement is kind of unusual.”

The downstream portion of Ditch 57 was improved in the 1970s, but the upper portion was in bad shape. Upstream farmers were losing crops to big rain events, which have become more common in recent years. However, downstream farmers objected to ditch changes that would increase water flow from the upper watershed.

To break the upstream-downstream impasse, local leaders devised a $1.2 million upgrade that incorporates many features new to agricultural drainage systems. These include:

A 3-acre surge pond in the middle of the drainage-way to store drainage water, reduce downstream peak flows and filter out sediment

An outlet weir to slow water discharge into the Cobb River

A two-stage open ditch design that mimics a natural floodplain, slowing water speed and trapping sediment

These innovations, along with a new 24-in. tile line at the top of the system and a 54-in. line in the middle, “improved upstream drainage without impeding downstream drainage,” says project engineer Chuck Brandel, I & S Group, Mankato, Minn. The changes will also cut sediment loss, a pressing water quality issue.

Brandel believes the approach used in Blue Earth County “could be repeated throughout the Midwest.” Beyond that, says Gary Sands, University of Minnesota Extension engineer, the project shows the “tremendous opportunity to look at these ditches as more than just ways to convey water.”

A history of conflict

Like many Midwest public drainage systems, Blue Earth County Ditch 57 was built in the early 20th century and has been spawning conflict and controversy its entire life.

Built between 1907 and 1921, the 5-mile-long, north-flowing waterway drains more than 6,000 acres of highly productive cropland – nearly all of it tiled. The last major improvements to the ditch were in 1976. By 2007, the upper portions were badly decayed: capacity was down to 50%, the 90-year-old concrete pipes were crumbling, and corrugated metal pipe in the middle of the system had collapsed.

The upland portions of Ditch 57’s watershed flooded regularly, says Pat Duncanson, Mapleton, Minn., who raises corn, soybeans and hogs. Every three or four years, he was forced to replant when the ditch overtopped its banks and inundated his land. In 2010, one of his most productive cornfields flooded three times due to water backup. Other farmers in the upper watershed had it even worse, Duncanson says.

The Duncansons and their upstream neighbors wanted to replace the upper and middle portions of the drainage system with an 84-in. tile line, but the downstream farmers said the ditch couldn’t handle that much additional water flow. “It quickly grew very contentious,” Duncanson says.

Yet, over the course of many meetings, leaders emerged who were committed to finding a workable compromise. “There were a lot of people who wanted to do the right thing,” Duncanson says.

In the process of working together to find a solution, neighbors set aside hard feelings from previous ditch conflicts, and casual acquaintances became good friends, says Dick Nienow, a retired farmer who owns land on the downstream portion of Ditch 57.

Water storage needed

The centerpiece of the Ditch 57 compromise is a 3-acre surge basin in the middle of the drainage-way that can store up to 26 acre-ft. of water. The reservoir meters out peak discharges, increasing upstream drainage capacity without overwhelming downstream capacity. “That was the only fair and ethical solution,” says Leo Getsfried, DNR area hydrologist. All public drainage improvements should “meet a standard of no increase in peak flows,” he says. From the beginning, Nienow adds, “that was one of our principal goals as farmers.”

Water storage basins are common on municipal storm water systems, but on a public ditch, “water storage on this scale is unprecedented,” says Austinson, the county ditch manager. One reason is price. Costs to acquire the land and build the storage structures on Ditch 57 topped $250,000. “Storage was essential,” Brandel says, “but the question was, how do we pay for it?”

The landowners, led by Duncanson and Nienow, worked for five years to obtain outside funding. It was a frustrating quest, and “we were very down at times,” Nienow says. Finally, a $485,000 grant from Minnesota’s Environment and Natural Resources Trust Fund, which supports water quality and conservation initiatives, allowed the project to proceed. “Outside funding was key to a compromise,” Duncanson says.

That’s the biggest hurdle to innovative conservation drainage projects like this one, Austinson adds. “Yes, it’s environmentally beneficial, but without the grant money, we couldn’t have done it.” Cost-share incentives have worked well for other water quality improvements on private lands, Nienow notes, and will likely be needed to make future conservation drainage projects feasible.

First test

Ditch 57 improvements were completed in fall 2011. The first test of the compromise design came May 4, when 3 in. of rain fell. The surge basin filled with water, peaking May 6, then emptied over the next 10 days. “We held the rain event in storage,” Brandel says, and “the water remained within the ditch banks.”

Throughout the Midwest, “There’s a huge backlog of public ditch systems that need to be improved,” says Getsfried, the DNR hydrologist. “This project may be in the vanguard.”

Water quality innovations on Ditch 57

Surge basin. The 3-acre, 9-ft.-deep pond stores 26 acre-ft. of drainage water from 1,700 acres. Ditch flow enters the basin through a 48-in. inlet and is discharged through a 15-in. outlet. Overflow weirs at the inlet and outlet prevent water from backing up in the ditch. The basin traps sediment and slows the flow of water into the lower portion of Ditch 57. The basin will need to be scraped out every 10-15 years.

The basin and 16-ft. buffers are planted with deep-rooted native grasses to hold the soil, filter sediment, and take up nutrients.

The surge basin is located about midway down the ditch in an area that often flooded in the past, says Project Engineer Chuck Brandel, I & S Group, Mankato. Minn. The site was not the first choice from a water management standpoint, he notes, but the preferred site was unavailable, and “the project leaders refused to force this on anybody. They felt it was important not to have animosity.” No wetlands were drained for the project.

Total water storage costs: $250,000

Outlet weir and water storage area. Ditch 57 empties into the Cobb River, and eventually flows into the Minnesota River. A 5-ft.-tall concrete weir, or dam, at the ditch outlet slows water discharge, dissipating its erosive force and allowing sediment to drop out. Drainage water backs up behind the weir into a 6.4-acre storage area within the channel. Stored water is slowly released into the river through an 18-in.-wide gap in the weir.

During a 3-in. rainstorm this spring, the weir prevented a water surge into the Cobb River, says Craig Austinson, Blue Earth County ditch manager. “I was really surprised at how well this worked. For something that cost just $15,000, this is an extremely effective method” of regulating peak drainage-water flows and preventing river-bank scouring, he says. Outlet weirs are a low-cost practice that could be added to many existing Midwest ditch systems, he adds.

Two-stage ditch. This 1,400-ft. open ditch mimics the floodplain of a natural stream. It’s designed to cut flooding, sediment transport and ditch-bank sloughing. The 2-ft.-wide main channel transports tile water from about 2,300 acres of cropland. Ten-ft.-wide grass “benches” on either side of the main channel slow water flow, allowing sediment to settle out without impeding drainage capacity.

Many public ditches could benefit from this modification, says University of Minnesota Extension Engineer Gary Sands. In fact, “Sometimes, a ditch will start to evolve to that form on its own, with a low flow channel and inside benches.”

Cost: $80,000

In-ditch sediment trap. A 3-ft.-deep trench excavated in a portion of the main ditch channel traps sediment from 2,300 acres of cropland. At $2/ft., “this is a very cost-effective way to store sediment and extend the ditch maintenance period,” Brandel says.

Native grass buffers. Grass buffer strips at least 16.5 ft. wide were planted along the entire length of Ditch 57, where there had been no buffers before. “I’m a big fan of buffers,” Austinson says, “not only for environmental reasons but for economic reasons, too.” Buffers cut erosion and lower ditch maintenance and repair costs, he says.

Instead of the usual blend of ditch grasses, more expensive native grasses were planted along Ditch 57. Native grasses’ advantage is deeper root systems to hold the banks and take up nutrients, Austinson says. A side benefit is wildlife habitat.